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swift-mirror/stdlib/public/runtime/Backtrace.cpp
Alastair Houghton 9d462a7b69 [Backtracing] Add an indication that we're working on a backtrace. 
When we crash, emit a message straight away that says we're working
on a backtrace.  If starting the backtracer fails, report that also.

Finally, add a duration to the messages output by the backtracer, so
that we can see how long it took.

rdar://118055527
2023-11-09 18:12:18 +00:00

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31 KiB
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//===--- Backtrace.cpp - Swift crash catching and backtracing support ---- ===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2022 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// Crash catching and backtracing support routines.
//
//===----------------------------------------------------------------------===//
#include <type_traits>
#include "llvm/ADT/StringRef.h"
#include "swift/Runtime/Config.h"
#include "swift/Runtime/Backtrace.h"
#include "swift/Runtime/Debug.h"
#include "swift/Runtime/Paths.h"
#include "swift/Runtime/EnvironmentVariables.h"
#include "swift/Runtime/Win32.h"
#include "swift/Demangling/Demangler.h"
#ifdef __linux__
#include <sys/auxv.h>
#endif
#ifdef _WIN32
#include <windows.h>
#else
#if __has_include(<sys/mman.h>)
#include <sys/mman.h>
#define PROTECT_BACKTRACE_SETTINGS 1
#else
#define PROTECT_BACKTRACE_SETTINGS 0
#warning Backtracer settings will not be protected in this configuration.
#endif
#if TARGET_OS_OSX || TARGET_OS_MACCATALYST
#include <spawn.h>
#endif
#include <unistd.h>
#endif
#include <cstdlib>
#include <cstring>
#include <cerrno>
#ifdef _WIN32
// We'll probably want dbghelp.h here
#else
#include <cxxabi.h>
#endif
#include "BacktracePrivate.h"
#define DEBUG_BACKTRACING_SETTINGS 0
#ifndef lengthof
#define lengthof(x) (sizeof(x) / sizeof(x[0]))
#endif
using namespace swift::runtime::backtrace;
namespace swift {
namespace runtime {
namespace backtrace {
SWIFT_RUNTIME_STDLIB_INTERNAL BacktraceSettings _swift_backtraceSettings = {
UnwindAlgorithm::Auto,
// enabled
#if TARGET_OS_OSX
OnOffTty::TTY,
#elif defined(__linux__) // || defined(_WIN32)
OnOffTty::On,
#else
OnOffTty::Off,
#endif
// demangle
true,
// interactive
#if TARGET_OS_OSX || defined(__linux__) // || defined(_WIN32)
OnOffTty::TTY,
#else
OnOffTty::Off,
#endif
// color
OnOffTty::TTY,
// timeout
30,
// threads
ThreadsToShow::Preset,
// registers
RegistersToShow::Preset,
// images
ImagesToShow::Preset,
// limit
64,
// top
16,
// sanitize,
SanitizePaths::Preset,
// preset
Preset::Auto,
// cache
true,
// outputTo,
OutputTo::Auto,
// swiftBacktracePath
NULL,
};
}
}
}
namespace {
class BacktraceInitializer {
public:
BacktraceInitializer();
};
SWIFT_ALLOWED_RUNTIME_GLOBAL_CTOR_BEGIN
BacktraceInitializer backtraceInitializer;
SWIFT_ALLOWED_RUNTIME_GLOBAL_CTOR_END
#if TARGET_OS_OSX || TARGET_OS_MACCATALYST
posix_spawnattr_t backtraceSpawnAttrs;
posix_spawn_file_actions_t backtraceFileActions;
#endif
#if SWIFT_BACKTRACE_ON_CRASH_SUPPORTED
// We need swiftBacktracePath to be aligned on a page boundary, and it also
// needs to be a multiple of the system page size.
#define SWIFT_BACKTRACE_BUFFER_SIZE 16384
static_assert((SWIFT_BACKTRACE_BUFFER_SIZE % SWIFT_PAGE_SIZE) == 0,
"The backtrace path buffer must be a multiple of the system "
"page size. If it isn't, you'll get weird crashes in other "
"code because we'll protect more than just the buffer.");
// The same goes for swiftBacktraceEnvironment
#define SWIFT_BACKTRACE_ENVIRONMENT_SIZE 32768
static_assert((SWIFT_BACKTRACE_ENVIRONMENT_SIZE % SWIFT_PAGE_SIZE) == 0,
"The environment buffer must be a multiple of the system "
"page size. If it isn't, you'll get weird crashes in other "
"code because we'll protect more than just the buffer.");
#if _WIN32
#pragma section(SWIFT_BACKTRACE_SECTION, read, write)
#if defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH)
const WCHAR swiftBacktracePath[] = L"" SWIFT_RUNTIME_FIXED_BACKTRACER_PATH;
#else
__declspec(allocate(SWIFT_BACKTRACE_SECTION)) WCHAR swiftBacktracePath[SWIFT_BACKTRACE_BUFFER_SIZE];
#endif // !defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH)
__declspec(allocate(SWIFT_BACKTRACE_SECTION)) CHAR swiftBacktraceEnv[SWIFT_BACKTRACE_ENVIRONMENT_SIZE];
#elif defined(__linux__) || TARGET_OS_OSX
#if defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH)
const char swiftBacktracePath[] = SWIFT_RUNTIME_FIXED_BACKTRACER_PATH;
#else
char swiftBacktracePath[SWIFT_BACKTRACE_BUFFER_SIZE] __attribute__((section(SWIFT_BACKTRACE_SECTION), aligned(SWIFT_PAGE_SIZE)));
#endif // !defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH
char swiftBacktraceEnv[SWIFT_BACKTRACE_ENVIRONMENT_SIZE] __attribute__((section(SWIFT_BACKTRACE_SECTION), aligned(SWIFT_PAGE_SIZE)));
#endif // defined(__linux__) || TARGET_OS_OSX
void _swift_backtraceSetupEnvironment();
bool isStdoutATty()
{
#ifndef _WIN32
return isatty(STDOUT_FILENO);
#else
DWORD dwMode;
return GetConsoleMode(GetStdHandle(STD_OUTPUT_HANDLE), &dwMode);
#endif
}
bool isStdinATty()
{
#ifndef _WIN32
return isatty(STDIN_FILENO);
#else
DWORD dwMode;
return GetConsoleMode(GetStdHandle(STD_INPUT_HANDLE), &dwMode);
#endif
}
#endif // SWIFT_BACKTRACE_ON_CRASH_SUPPORTED
void _swift_processBacktracingSetting(llvm::StringRef key, llvm::StringRef value);
void _swift_parseBacktracingSettings(const char *);
#if DEBUG_BACKTRACING_SETTINGS
const char *algorithmToString(UnwindAlgorithm algorithm) {
switch (algorithm) {
case UnwindAlgorithm::Auto: return "Auto";
case UnwindAlgorithm::Fast: return "Fast";
case UnwindAlgorithm::Precise: return "Precise";
}
}
const char *onOffTtyToString(OnOffTty oot) {
switch (oot) {
case OnOffTty::On: return "On";
case OnOffTty::Off: return "Off";
case OnOffTty::TTY: return "TTY";
}
}
const char *boolToString(bool b) {
return b ? "true" : "false";
}
const char *presetToString(Preset preset) {
switch (preset) {
case Preset::Auto: return "Auto";
case Preset::Friendly: return "Friendly";
case Preset::Medium: return "Medium";
case Preset::Full: return Full;
}
}
#endif
#ifdef __linux__
bool isPrivileged() {
return getauxval(AT_SECURE);
}
#elif defined(__APPLE__) || defined(__FreeBSD__) || defined(__OpenBSD__)
bool isPrivileged() {
return issetugid();
}
#elif _WIN32
bool isPrivileged() {
return false;
}
#endif
} // namespace
BacktraceInitializer::BacktraceInitializer() {
const char *backtracing = swift::runtime::environment::SWIFT_BACKTRACE();
// Force off for setuid processes.
if (isPrivileged()) {
_swift_backtraceSettings.enabled = OnOffTty::Off;
}
if (backtracing)
_swift_parseBacktracingSettings(backtracing);
#if !SWIFT_BACKTRACE_ON_CRASH_SUPPORTED
if (_swift_backtraceSettings.enabled != OnOffTty::Off) {
swift::warning(0,
"swift runtime: backtrace-on-crash is not supported on "
"this platform.\n");
_swift_backtraceSettings.enabled = OnOffTty::Off;
}
#else
if (isPrivileged() && _swift_backtraceSettings.enabled != OnOffTty::Off) {
// You'll only see this warning if you do e.g.
//
// SWIFT_BACKTRACE=enable=on /path/to/some/setuid/binary
//
// as opposed to
//
// /path/to/some/setuid/binary
//
// i.e. when you're trying to force matters.
swift::warning(0,
"swift runtime: backtrace-on-crash is not supported for "
"privileged executables.\n");
_swift_backtraceSettings.enabled = OnOffTty::Off;
}
if (_swift_backtraceSettings.enabled == OnOffTty::TTY)
_swift_backtraceSettings.enabled =
isStdoutATty() ? OnOffTty::On : OnOffTty::Off;
if (_swift_backtraceSettings.interactive == OnOffTty::TTY) {
_swift_backtraceSettings.interactive =
(isStdoutATty() && isStdinATty()) ? OnOffTty::On : OnOffTty::Off;
}
if (_swift_backtraceSettings.color == OnOffTty::TTY)
_swift_backtraceSettings.color =
isStdoutATty() ? OnOffTty::On : OnOffTty::Off;
if (_swift_backtraceSettings.preset == Preset::Auto) {
if (_swift_backtraceSettings.interactive == OnOffTty::On)
_swift_backtraceSettings.preset = Preset::Friendly;
else
_swift_backtraceSettings.preset = Preset::Full;
}
if (_swift_backtraceSettings.outputTo == OutputTo::Auto) {
if (_swift_backtraceSettings.interactive == OnOffTty::On)
_swift_backtraceSettings.outputTo = OutputTo::Stdout;
else
_swift_backtraceSettings.outputTo = OutputTo::Stderr;
}
#if !defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH)
if (_swift_backtraceSettings.enabled == OnOffTty::On
&& !_swift_backtraceSettings.swiftBacktracePath) {
_swift_backtraceSettings.swiftBacktracePath
= swift_copyAuxiliaryExecutablePath("swift-backtrace");
if (!_swift_backtraceSettings.swiftBacktracePath) {
// Disabled warning for now - rdar://106813646
/* swift::warning(0,
"swift runtime: unable to locate swift-backtrace; "
"disabling backtracing.\n"); */
_swift_backtraceSettings.enabled = OnOffTty::Off;
}
}
#endif
if (_swift_backtraceSettings.enabled == OnOffTty::On) {
// Copy the path to swift-backtrace into swiftBacktracePath, then write
// protect it so that it can't be overwritten easily at runtime. We do
// this to avoid creating a massive security hole that would allow an
// attacker to overwrite the path and then cause a crash to get us to
// execute an arbitrary file.
#if _WIN32
if (_swift_backtraceSettings.algorithm == UnwindAlgorithm::Auto)
_swift_backtraceSettings.algorithm = UnwindAlgorithm::Precise;
#if !defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH)
int len = ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS,
_swift_backtraceSettings.swiftBacktracePath, -1,
swiftBacktracePath,
SWIFT_BACKTRACE_BUFFER_SIZE);
if (!len) {
swift::warning(0,
"swift runtime: unable to convert path to "
"swift-backtrace: %08lx; disabling backtracing.\n",
::GetLastError());
_swift_backtraceSettings.enabled = OnOffTty::Off;
} else if (!VirtualProtect(swiftBacktracePath,
sizeof(swiftBacktracePath),
PAGE_READONLY,
NULL)) {
swift::warning(0,
"swift runtime: unable to protect path to "
"swift-backtrace: %08lx; disabling backtracing.\n",
::GetLastError());
_swift_backtraceSettings.enabled = OnOffTty::Off;
}
#endif // !defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH)
_swift_backtraceSetupEnvironment();
if (!VirtualProtect(swiftBacktraceEnv,
sizeof(swiftBacktraceEnv),
PAGE_READONLY,
NULL)) {
swift::warning(0,
"swift runtime: unable to protect environment "
"for swift-backtrace: %08lx; disabling backtracing.\n",
::GetLastError());
_swift_backtraceSettings.enabled = OnOffTty::Off;
}
#else
if (_swift_backtraceSettings.algorithm == UnwindAlgorithm::Auto)
_swift_backtraceSettings.algorithm = UnwindAlgorithm::Precise;
#if !defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH)
size_t len = strlen(_swift_backtraceSettings.swiftBacktracePath);
if (len > SWIFT_BACKTRACE_BUFFER_SIZE - 1) {
swift::warning(0,
"swift runtime: path to swift-backtrace is too long; "
"disabling backtracing.\n");
_swift_backtraceSettings.enabled = OnOffTty::Off;
} else {
memcpy(swiftBacktracePath,
_swift_backtraceSettings.swiftBacktracePath,
len + 1);
#if PROTECT_BACKTRACE_SETTINGS
if (mprotect(swiftBacktracePath,
sizeof(swiftBacktracePath),
PROT_READ) < 0) {
swift::warning(0,
"swift runtime: unable to protect path to "
"swift-backtrace at %p: %d; disabling backtracing.\n",
swiftBacktracePath,
errno);
_swift_backtraceSettings.enabled = OnOffTty::Off;
}
#endif // PROTECT_BACKTRACE_SETTINGS
}
#endif // !defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH)
_swift_backtraceSetupEnvironment();
#if PROTECT_BACKTRACE_SETTINGS
if (mprotect(swiftBacktraceEnv,
sizeof(swiftBacktraceEnv),
PROT_READ) < 0) {
swift::warning(0,
"swift runtime: unable to protect environment for "
"swift-backtrace at %p: %d; disabling backtracing.\n",
swiftBacktraceEnv,
errno);
_swift_backtraceSettings.enabled = OnOffTty::Off;
}
#endif // PROTECT_BACKTRACE_SETTINGS
#endif // !_WIN32
}
if (_swift_backtraceSettings.enabled == OnOffTty::On) {
#if TARGET_OS_OSX || TARGET_OS_MACCATALYST
// Make sure that all fds are closed except for stdin/stdout/stderr.
posix_spawnattr_init(&backtraceSpawnAttrs);
posix_spawnattr_setflags(&backtraceSpawnAttrs, POSIX_SPAWN_CLOEXEC_DEFAULT);
posix_spawn_file_actions_init(&backtraceFileActions);
posix_spawn_file_actions_addinherit_np(&backtraceFileActions, STDIN_FILENO);
posix_spawn_file_actions_addinherit_np(&backtraceFileActions, STDOUT_FILENO);
posix_spawn_file_actions_addinherit_np(&backtraceFileActions, STDERR_FILENO);
#endif
ErrorCode err = _swift_installCrashHandler();
if (err != 0) {
swift::warning(0,
"swift runtime: crash handler installation failed; "
"disabling backtracing.\n");
}
}
#endif
#if DEBUG_BACKTRACING_SETTINGS
printf("\nBACKTRACING SETTINGS\n"
"\n"
"algorithm: %s\n"
"enabled: %s\n"
"demangle: %s\n"
"interactive: %s\n"
"color: %s\n"
"timeout: %u\n"
"preset: %s\n"
"swiftBacktracePath: %s\n",
algorithmToString(_swift_backtraceSettings.algorithm),
onOffTtyToString(_swift_backtraceSettings.enabled),
boolToString(_swift_backtraceSettings.demangle),
onOffTtyToString(_swift_backtraceSettings.interactive),
onOffTtyToString(_swift_backtraceSettings.color),
_swift_backtraceSettings.timeout,
presetToString(_swift_backtraceSettings.preset),
swiftBacktracePath);
printf("\nBACKTRACING ENV\n");
const char *ptr = swiftBacktraceEnv;
while (*ptr) {
size_t len = std::strlen(ptr);
printf("%s\n", ptr);
ptr += len + 1;
}
printf("\n");
#endif
}
namespace {
OnOffTty
parseOnOffTty(llvm::StringRef value)
{
if (value.equals_insensitive("on")
|| value.equals_insensitive("true")
|| value.equals_insensitive("yes")
|| value.equals_insensitive("y")
|| value.equals_insensitive("t")
|| value.equals_insensitive("1"))
return OnOffTty::On;
if (value.equals_insensitive("tty")
|| value.equals_insensitive("auto"))
return OnOffTty::TTY;
return OnOffTty::Off;
}
bool
parseBoolean(llvm::StringRef value)
{
return (value.equals_insensitive("on")
|| value.equals_insensitive("true")
|| value.equals_insensitive("yes")
|| value.equals_insensitive("y")
|| value.equals_insensitive("t")
|| value.equals_insensitive("1"));
}
void
_swift_processBacktracingSetting(llvm::StringRef key,
llvm::StringRef value)
{
if (key.equals_insensitive("enable")) {
_swift_backtraceSettings.enabled = parseOnOffTty(value);
} else if (key.equals_insensitive("demangle")) {
_swift_backtraceSettings.demangle = parseBoolean(value);
} else if (key.equals_insensitive("interactive")) {
_swift_backtraceSettings.interactive = parseOnOffTty(value);
} else if (key.equals_insensitive("color")) {
_swift_backtraceSettings.color = parseOnOffTty(value);
} else if (key.equals_insensitive("timeout")) {
int count;
llvm::StringRef valueCopy = value;
if (value.equals_insensitive("none")) {
_swift_backtraceSettings.timeout = 0;
} else if (!valueCopy.consumeInteger(0, count)) {
// Yes, consumeInteger() really does return *false* for success
llvm::StringRef unit = valueCopy.trim();
if (unit.empty()
|| unit.equals_insensitive("s")
|| unit.equals_insensitive("seconds"))
_swift_backtraceSettings.timeout = count;
else if (unit.equals_insensitive("m")
|| unit.equals_insensitive("minutes"))
_swift_backtraceSettings.timeout = count * 60;
else if (unit.equals_insensitive("h")
|| unit.equals_insensitive("hours"))
_swift_backtraceSettings.timeout = count * 3600;
if (_swift_backtraceSettings.timeout < 0) {
swift::warning(0,
"swift runtime: bad backtracing timeout %ds\n",
_swift_backtraceSettings.timeout);
_swift_backtraceSettings.timeout = 0;
}
} else {
swift::warning(0,
"swift runtime: bad backtracing timeout '%.*s'\n",
static_cast<int>(value.size()), value.data());
}
} else if (key.equals_insensitive("unwind")) {
if (value.equals_insensitive("auto"))
_swift_backtraceSettings.algorithm = UnwindAlgorithm::Auto;
else if (value.equals_insensitive("fast"))
_swift_backtraceSettings.algorithm = UnwindAlgorithm::Fast;
else if (value.equals_insensitive("precise"))
_swift_backtraceSettings.algorithm = UnwindAlgorithm::Precise;
else {
swift::warning(0,
"swift runtime: unknown unwind algorithm '%.*s'\n",
static_cast<int>(value.size()), value.data());
}
} else if (key.equals_insensitive("sanitize")) {
_swift_backtraceSettings.sanitize
= parseBoolean(value) ? SanitizePaths::On : SanitizePaths::Off;
} else if (key.equals_insensitive("preset")) {
if (value.equals_insensitive("auto"))
_swift_backtraceSettings.preset = Preset::Auto;
else if (value.equals_insensitive("friendly"))
_swift_backtraceSettings.preset = Preset::Friendly;
else if (value.equals_insensitive("medium"))
_swift_backtraceSettings.preset = Preset::Medium;
else if (value.equals_insensitive("full"))
_swift_backtraceSettings.preset = Preset::Full;
else {
swift::warning(0,
"swift runtime: unknown backtracing preset '%.*s'\n",
static_cast<int>(value.size()), value.data());
}
} else if (key.equals_insensitive("threads")) {
if (value.equals_insensitive("all"))
_swift_backtraceSettings.threads = ThreadsToShow::All;
else if (value.equals_insensitive("crashed"))
_swift_backtraceSettings.threads = ThreadsToShow::Crashed;
else {
swift::warning(0,
"swift runtime: unknown threads setting '%.*s'\n",
static_cast<int>(value.size()), value.data());
}
} else if (key.equals_insensitive("registers")) {
if (value.equals_insensitive("none"))
_swift_backtraceSettings.registers = RegistersToShow::None;
else if (value.equals_insensitive("all"))
_swift_backtraceSettings.registers = RegistersToShow::All;
else if (value.equals_insensitive("crashed"))
_swift_backtraceSettings.registers = RegistersToShow::Crashed;
else {
swift::warning(0,
"swift runtime: unknown registers setting '%.*s'\n",
static_cast<int>(value.size()), value.data());
}
} else if (key.equals_insensitive("images")) {
if (value.equals_insensitive("none"))
_swift_backtraceSettings.images = ImagesToShow::None;
else if (value.equals_insensitive("all"))
_swift_backtraceSettings.images = ImagesToShow::All;
else if (value.equals_insensitive("mentioned"))
_swift_backtraceSettings.images = ImagesToShow::Mentioned;
else {
swift::warning(0,
"swift runtime: unknown registers setting '%.*s'\n",
static_cast<int>(value.size()), value.data());
}
} else if (key.equals_insensitive("limit")) {
int limit;
// Yes, getAsInteger() returns false for success.
if (value.equals_insensitive("none"))
_swift_backtraceSettings.limit = -1;
else if (!value.getAsInteger(0, limit) && limit > 0)
_swift_backtraceSettings.limit = limit;
else {
swift::warning(0,
"swift runtime: bad backtrace limit '%.*s'\n",
static_cast<int>(value.size()), value.data());
}
} else if (key.equals_insensitive("top")) {
int top;
// (If you think the next line is wrong, see above.)
if (!value.getAsInteger(0, top) && top >= 0)
_swift_backtraceSettings.top = top;
else {
swift::warning(0,
"swift runtime: bad backtrace top count '%.*s'\n",
static_cast<int>(value.size()), value.data());
}
} else if (key.equals_insensitive("cache")) {
_swift_backtraceSettings.cache = parseBoolean(value);
} else if (key.equals_insensitive("output-to")) {
if (value.equals_insensitive("auto"))
_swift_backtraceSettings.outputTo = OutputTo::Auto;
else if (value.equals_insensitive("stdout"))
_swift_backtraceSettings.outputTo = OutputTo::Stdout;
else if (value.equals_insensitive("stderr"))
_swift_backtraceSettings.outputTo = OutputTo::Stderr;
else {
swift::warning(0,
"swift runtime: unknown output-to setting '%.*s'\n",
static_cast<int>(value.size()), value.data());
}
#if !defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH)
} else if (key.equals_insensitive("swift-backtrace")) {
size_t len = value.size();
char *path = (char *)std::malloc(len + 1);
std::copy(value.begin(), value.end(), path);
path[len] = 0;
std::free(const_cast<char *>(_swift_backtraceSettings.swiftBacktracePath));
_swift_backtraceSettings.swiftBacktracePath = path;
#endif // !defined(SWIFT_RUNTIME_FIXED_BACKTRACER_PATH)
} else {
swift::warning(0,
"swift runtime: unknown backtracing setting '%.*s'\n",
static_cast<int>(key.size()), key.data());
}
}
void
_swift_parseBacktracingSettings(const char *settings)
{
const char *ptr = settings;
const char *key = ptr;
const char *keyEnd;
const char *value;
const char *valueEnd;
enum {
ScanningKey,
ScanningValue
} state = ScanningKey;
int ch;
while ((ch = *ptr++)) {
switch (state) {
case ScanningKey:
if (ch == '=') {
keyEnd = ptr - 1;
value = ptr;
state = ScanningValue;
continue;
}
break;
case ScanningValue:
if (ch == ',') {
valueEnd = ptr - 1;
_swift_processBacktracingSetting(llvm::StringRef(key, keyEnd - key),
llvm::StringRef(value,
valueEnd - value));
key = ptr;
state = ScanningKey;
continue;
}
break;
}
}
if (state == ScanningValue) {
valueEnd = ptr - 1;
_swift_processBacktracingSetting(llvm::StringRef(key, keyEnd - key),
llvm::StringRef(value,
valueEnd - value));
}
}
#if SWIFT_BACKTRACE_ON_CRASH_SUPPORTED
// These are the only environment variables that are passed through to
// the swift-backtrace process. They're copied at program start, and then
// write protected so they can't be manipulated by an attacker using a buffer
// overrun.
const char * const environmentVarsToPassThrough[] = {
"LD_LIBRARY_PATH",
"DYLD_LIBRARY_PATH",
"DYLD_FRAMEWORK_PATH",
"PATH",
"TERM",
"LANG",
"HOME"
};
#define BACKTRACE_MAX_ENV_VARS lengthof(environmentVarsToPassThrough)
void
_swift_backtraceSetupEnvironment()
{
size_t remaining = sizeof(swiftBacktraceEnv);
char *penv = swiftBacktraceEnv;
std::memset(swiftBacktraceEnv, 0, sizeof(swiftBacktraceEnv));
// We definitely don't want this on in the swift-backtrace program
const char * const disable = "SWIFT_BACKTRACE=enable=no";
const size_t disableLen = std::strlen(disable) + 1;
std::memcpy(penv, disable, disableLen);
penv += disableLen;
remaining -= disableLen;
for (unsigned n = 0; n < BACKTRACE_MAX_ENV_VARS; ++n) {
const char *name = environmentVarsToPassThrough[n];
const char *value = getenv(name);
if (!value)
continue;
size_t nameLen = std::strlen(name);
size_t valueLen = std::strlen(value);
size_t totalLen = nameLen + 1 + valueLen + 1;
if (remaining > totalLen) {
std::memcpy(penv, name, nameLen);
penv += nameLen;
*penv++ = '=';
std::memcpy(penv, value, valueLen);
penv += valueLen;
*penv++ = 0;
remaining -= totalLen;
}
}
*penv = 0;
}
#ifdef __linux__
struct spawn_info {
const char *path;
char * const *argv;
char * const *envp;
int memserver;
};
uint8_t spawn_stack[4096] __attribute__((aligned(SWIFT_PAGE_SIZE)));
int
do_spawn(void *ptr) {
struct spawn_info *pinfo = (struct spawn_info *)ptr;
/* Ensure that the memory server is always on fd 4 */
if (pinfo->memserver != 4) {
dup2(pinfo->memserver, 4);
close(pinfo->memserver);
}
/* Clear the signal mask */
sigset_t mask;
sigfillset(&mask);
sigprocmask(SIG_UNBLOCK, &mask, NULL);
return execvpe(pinfo->path, pinfo->argv, pinfo->envp);
}
int
safe_spawn(pid_t *ppid, const char *path, int memserver,
char * const argv[], char * const envp[])
{
struct spawn_info info = { path, argv, envp, memserver };
/* The CLONE_VFORK is *required* because info is on the stack; we don't
want to return until *after* the subprocess has called execvpe(). */
int ret = clone(do_spawn, spawn_stack + sizeof(spawn_stack),
CLONE_VFORK|CLONE_VM, &info);
if (ret < 0)
return ret;
close(memserver);
*ppid = ret;
return 0;
}
#endif // defined(__linux__)
#endif // SWIFT_BACKTRACE_ON_CRASH_SUPPORTED
} // namespace
namespace swift {
namespace runtime {
namespace backtrace {
/// Test if a Swift symbol name represents a thunk function.
///
/// In backtraces, it is often desirable to omit thunk frames as they usually
/// just clutter up the backtrace unnecessarily.
///
/// @param mangledName is the symbol name to be tested.
///
/// @returns `true` if `mangledName` represents a thunk function.
SWIFT_RUNTIME_STDLIB_SPI bool
_swift_backtrace_isThunkFunction(const char *mangledName) {
swift::Demangle::Context ctx;
return ctx.isThunkSymbol(mangledName);
}
// Try to demangle a symbol.
SWIFT_RUNTIME_STDLIB_SPI char *
_swift_backtrace_demangle(const char *mangledName,
size_t mangledNameLength,
char *outputBuffer,
size_t *outputBufferSize) {
llvm::StringRef name = llvm::StringRef(mangledName, mangledNameLength);
// You must provide buffer size if you're providing your own output buffer
if (outputBuffer && !outputBufferSize) {
return nullptr;
}
if (Demangle::isSwiftSymbol(name)) {
// This is a Swift mangling
auto options = DemangleOptions::SimplifiedUIDemangleOptions();
auto result = Demangle::demangleSymbolAsString(name, options);
size_t bufferSize;
if (outputBufferSize) {
bufferSize = *outputBufferSize;
*outputBufferSize = result.length() + 1;
}
if (outputBuffer == nullptr) {
outputBuffer = (char *)::malloc(result.length() + 1);
bufferSize = result.length() + 1;
}
size_t toCopy = std::min(bufferSize - 1, result.length());
::memcpy(outputBuffer, result.data(), toCopy);
outputBuffer[toCopy] = '\0';
return outputBuffer;
#ifndef _WIN32
} else if (name.startswith("_Z")) {
// Try C++; note that we don't want to force callers to use malloc() to
// allocate their buffer, which is a requirement for __cxa_demangle
// because it may call realloc() on the incoming pointer. As a result,
// we never pass the caller's buffer to __cxa_demangle.
size_t resultLen;
int status = 0;
char *result = abi::__cxa_demangle(mangledName, nullptr, &resultLen, &status);
if (result) {
size_t bufferSize;
if (outputBufferSize) {
bufferSize = *outputBufferSize;
*outputBufferSize = resultLen;
}
if (outputBuffer == nullptr) {
return result;
}
size_t toCopy = std::min(bufferSize - 1, resultLen - 1);
::memcpy(outputBuffer, result, toCopy);
outputBuffer[toCopy] = '\0';
free(result);
return outputBuffer;
}
#else
// On Windows, the mangling is different.
// ###TODO: Call __unDName()
#endif
}
return nullptr;
}
// N.B. THIS FUNCTION MUST BE SAFE TO USE FROM A CRASH HANDLER. On Linux
// and macOS, that means it must be async-signal-safe. On Windows, there
// isn't an equivalent notion but a similar restriction applies.
SWIFT_RUNTIME_STDLIB_INTERNAL bool
#ifdef __linux__
_swift_spawnBacktracer(const ArgChar * const *argv, int memserver_fd)
#else
_swift_spawnBacktracer(const ArgChar * const *argv)
#endif
{
#if !SWIFT_BACKTRACE_ON_CRASH_SUPPORTED
return false;
#elif TARGET_OS_OSX || TARGET_OS_MACCATALYST || defined(__linux__)
pid_t child;
const char *env[BACKTRACE_MAX_ENV_VARS + 1];
// Set-up the environment array
const char *ptr = swiftBacktraceEnv;
unsigned nEnv = 0;
while (*ptr && nEnv < lengthof(env) - 1) {
env[nEnv++] = ptr;
ptr += std::strlen(ptr) + 1;
};
env[nEnv] = 0;
// SUSv3 says argv and envp are "completely constant" and that the reason
// posix_spawn() et al use char * const * is for compatibility.
#ifdef __linux__
int ret = safe_spawn(&child, swiftBacktracePath, memserver_fd,
const_cast<char * const *>(argv),
const_cast<char * const *>(env));
#else
int ret = posix_spawn(&child, swiftBacktracePath,
&backtraceFileActions, &backtraceSpawnAttrs,
const_cast<char * const *>(argv),
const_cast<char * const *>(env));
#endif
if (ret < 0)
return false;
int wstatus;
do {
ret = waitpid(child, &wstatus, 0);
} while (ret < 0 && errno == EINTR);
if (WIFEXITED(wstatus))
return WEXITSTATUS(wstatus) == 0;
return false;
// ###TODO: Windows
#endif
}
// N.B. THIS FUNCTION MUST BE SAFE TO USE FROM A CRASH HANDLER. On Linux
// and macOS, that means it must be async-signal-safe. On Windows, there
// isn't an equivalent notion but a similar restriction applies.
SWIFT_RUNTIME_STDLIB_INTERNAL void
_swift_displayCrashMessage(int signum, const void *pc)
{
#if !SWIFT_BACKTRACE_ON_CRASH_SUPPORTED
return;
#else
int fd = STDOUT_FILENO;
if (_swift_backtraceSettings.outputTo == OutputTo::Stderr)
fd = STDERR_FILENO;
const char *intro;
if (_swift_backtraceSettings.color == OnOffTty::On) {
intro = "\n💣 \033[91mProgram crashed: ";
} else {
intro = "\n*** Program crashed: ";
}
write(fd, intro, strlen(intro));
char sigbuf[30];
strcpy(sigbuf, "Signal ");
_swift_formatUnsigned((unsigned)signum, sigbuf + 7);
write(fd, sigbuf, strlen(sigbuf));
const char *message;
if (!pc) {
message = ": Backtracing";
} else {
message = ": Backtracing from 0x";
}
write(fd, message, strlen(message));
if (pc) {
char pcbuf[18];
_swift_formatAddress(pc, pcbuf);
write(fd, pcbuf, strlen(pcbuf));
}
const char *outro;
if (_swift_backtraceSettings.color == OnOffTty::On) {
outro = "...\033[0m";
} else {
outro = "...";
}
write(fd, outro, strlen(outro));
#endif
}
} // namespace backtrace
} // namespace runtime
} // namespace swift
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